Fly mask



FIG. 1 is a perspective view of a fly mask showing my new design, the broken lines showing a horse's head are for illustrative purposes only and form no part of the claimed design;

FIG. 2 is a perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a left side elevational view thereof, the undisclosed right side being a mirror image;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a rear elevational view thereof. 

The ornamental design for a fly mask, as shown and described. 